The present invention relates to a starter motor of an overhang type structure for starting an engine and, particularly, to an improvement of a pinion stopper thereof.
FIG. 6 is a cross section of a conventional engine starter motor having an overhang structure, in which a stopper 11 is assembled to an output shaft 15 of the motor through a ring 6. A pinion 17 is formed on an outer peripheral surface of the output shaft 15 and is assembled to an over-running clutch 14.
A bearing 9 is supported by an inner periphery of the pinion 7 and receives a reaction force from the output shaft 5. The inner peripheral surface of the pinion 17 is formed with a step portion 7a which serves to restrict a movement of the pinion 17 by a contact with the stopper 11.
A bearing 8 is received in and supported by a recess of a front bracket 10, which supports the pinion 17 slidably. A magnet switch 1 is disposed on a rear end of the front bracket 10 and a plunger 2 is arranged on an inner surface side of the switch 1. The plunger 2 functions to move the over-running clutch 4 forward through a lever 3.
In operation, when a voltage is applied to the magnet switch 1, the plunger 2 is attracted to move the over-running clutch 14 forward through the lever 3 to thereby move the pinion 17 through the bearing 8 so that a teethed portion of the pinion 17 meshes with a ring gear of an engine (not shown).
A distance along which the pinion 17 can move is restricted by a contact between the inner step portion 7a of the pinion 17 and the stopper 11.
In order to assemble the stopper 11 to the output shaft 2, it is necessary to protrude a front end portion of the stopper 11 slightly from the pinion and a front end of the output shaft 12 protrudes from the pinion end, necessarily, resulting in a total length of the starter motor large enough to make the assembling thereof to the engine difficult. Further, a freedom of design of the starter motor is restricted by the fact that the stopper 11 is assembled to the output shaft 5 through a ring 6, causing a reduction of an outer diameter of the stopper 11 to a certain value to be impossible in view of mechanical strength thereof and, therefore, in order to keep the strength of root portion of pinion teeth, it is very difficult to reduce the number of teeth of the pinion 17. Further, the assembling and disassembling of the stopper 11 with respect to the output shaft is complicated and troublesome.